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1
LEU, TZONG-SHYNG, and CHING-YI PAI. "PARTICLE-FREE EXTRACTION BY USING MICROCHANNEL STRUCTURES." International Journal of Modern Physics: Conference Series 19 (January 2012): 237–41. http://dx.doi.org/10.1142/s201019451200880x.
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Modern separation methods of particles are usually prepared by large equipments. In this study, microfluidic chips with backward-facing-step (BFS) microchannel structures and centrifugal force are used to extract particle-free fluid from physical samples at the branch. Numerical simulation and experimental studies were performed to investigate the effects of inlet Reynolds number ( Re 0), as well as the particle-free fluid outlet Reynolds number ( Re 1), on the minimum radius of particles (R) that can be excluded from the particle-free fluid outlet channel. The fraction of the volumetric flow rate of particle-free extraction α (=extraction flow rate/inlet flow rate) was also obtained to evaluate the efficiency of particle-free extraction. Based on the numerical and experimental results, it is found that the design with 90° elbow inlet channel has a better performance than straight inlet channel. In this experiment, 1.0 μm radius of particles can be successfully separated from the fluid, and the volumetric fraction of the extraction flow rate was approximately 1.8% when inlet and outlet Reynolds numbers are 90 and 3.0 respectively.
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Orozco, Luisa Fernanda, Jean-Yves Delenne, Philippe Sornay, and Farhang Radjai. "Effect of particle shape on particle breakage inside rotating cylinders." EPJ Web of Conferences 249 (2021): 07002. http://dx.doi.org/10.1051/epjconf/202124907002.
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We study the influence of particle shape on the evolution of particle breakage process taking place inside rotating cylinders. Extensive particle dynamics simulations taking into account the dynamics of the granular flow, particle breakage, and polygonal particle shapes were carried out. We find that the rate of particle breakage is faster in samples composed of initially rounder particles. The analysis of the active flowing layer thickness suggests that for samples composed of rounder particles a relatively lower dilatancy and higher connectivity lead to a less curved free surface profile. As a result, rounder particles rolling down the free surface have a higher mobility and thus higher velocities. In consequence, the faster breakage observed for rounder initial particles is due to the larger particles kinetic energy at the toe of the flow.
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Good, R. H. "‘‘Free‐particle’’ software." American Journal of Physics 54, no. 12 (1986): 1064. http://dx.doi.org/10.1119/1.14737.
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Donzel, Lise, Martin Seeger, Daniel Over, and Jan Carstensen. "Metallic Particle Motion and Breakdown at AC Voltages in CO2/O2 and SF6." Energies 15, no. 8 (2022): 2804. http://dx.doi.org/10.3390/en15082804.
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This study deals with gaseous insulation contaminated by free moving particles. Two gases were investigated: SF6 (0.45 MPa) and a CO2/O2 gas mixture (0.75 MPa). Video recordings were used to track a free particle moving between a plate and a Rogowski electrode for validation of a 1D particle motion model. The effect of fixed and free particles (4 or 8 mm, Ø 0.9 mm) on the breakdown voltage and the mean time between breakdowns was determined in a concentric set of electrodes. The value of the breakdown voltage for a free particle was between those of a particle fixed to the enclosure and the central electrode. The particle motion in the concentric case could not be observed in the experimental set-up and was therefore simulated using a 1D model. For the 4 mm free particle, the breakdown seemed to be initiated in the inter-electrode gap in CO2 and at the crossing in SF6, while for the 8 mm particle, breakdown occurred at lift-off in both gases. A parameter k describing the width of the time to breakdown distribution was introduced. A low value of k was associated with the breakdown from the particles at the electrodes, while k was larger than 10 when the breakdown was decided during particle flight.
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Jiang, Fang, and Guo Guang Cheng. "Inclusion Removal at the Free Surface of Steel Bath by Bubble Flotation." Advanced Materials Research 399-401 (November 2011): 216–22. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.216.
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In the present work, physical model experiments were carried out to clarify the inclusion removal at the free surface of steel bath. Polyethylene particles were used to simulate the non-wetting inclusions like alumina and silica. The influence of gas flow rate and bubble size on the inclusion removal at the free surface was evaluated. It is demonstrated that not all particles are removed when they arrive at the free surface of liquid bath, and those which are not removed will get back to the bath. It is found an annular particle layer is formed by the removed particles at free surface, which can capture other particles arriving at the free surface. However, the attachment of particles to the annular particle layer is not stable, and re-entrainment of particles occurs at high gas flow rate. It is shown the overall particle removal is determined by a balance of removal and re-entrainment. The particle removal constant increases with the increase in the gas flow rate, but decreases with the increase in bubble size. The equilibrium concentration of particles increases with the increase in gas flow rate and bubble size.
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Light, Adam D., Hariharan Srinivasulu, Christopher J. Hansen, and Michael R. Brown. "Counterintuitive Particle Confinement in a Helical Force-Free Plasma." Plasma 8, no. 2 (2025): 20. https://doi.org/10.3390/plasma8020020.
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The force-free magnetic field solution formed in a high-aspect ratio cylinder is a non-axisymmetric (m=1), closed magnetic structure that can be produced in laboratory experiments. Force-free equilibria can have strong field gradients that break the usual adiabatic invariants associated with particle motion, and gyroradii at measured conditions can be large relative to the gradient scale lengths of the magnetic field. Individual particle motion is largely unexplored in force-free systems without axisymmetry, and it is unclear how the large gradients influence confinement. To understand more about how particles remain confined in these configurations, we simulate a thermal distribution of protons moving in a high-aspect-ratio force-free magnetic field using a Boris stepper. The particle loss is logarithmic in time, which suggests trapping and/or periodic orbits. Many particles do remain confined in particular regions of the field, analogous to trapped particles in other magnetic configurations. Some closed flux surfaces can be identified, but particle orbits are not necessarily described by these surfaces. We show examples of orbits that remain on well-defined surfaces and discuss the statistical properties of confined and escaping particles.
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Yung, Cheuk-Man, Christopher S. Ward, Katherine M. Davis, Zackary I. Johnson, and Dana E. Hunt. "Insensitivity of Diverse and Temporally Variable Particle-Associated Microbial Communities to Bulk Seawater Environmental Parameters." Applied and Environmental Microbiology 82, no. 11 (2016): 3431–37. http://dx.doi.org/10.1128/aem.00395-16.
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ABSTRACTThere is a growing recognition of the roles of marine microenvironments as reservoirs of biodiversity and as sites of enhanced biological activity and in facilitating biological interactions. Here, we examine the bacterial community inhabiting free-living and particle-associated seawater microenvironments at the Pivers Island Coastal Observatory (PICO). 16S rRNA gene libraries from monthly samples (July 2013 to August 2014) were used to identify microbes in seawater in four size fractions: >63 μm (zooplankton and large particles), 63 to 5 μm (particles), 5 to 1 μm (small particles/dividing cells), and <1 μm (free-living prokaryotes). Analyses of microbial community composition highlight the importance of the microhabitat (e.g., particle-associated versus free-living lifestyle) as communities cluster by size fraction, and the microhabitat explains more of the community variability than measured environmental parameters, including pH, particle concentration, projected daily insolation, nutrients, and temperature. While temperature is statistically associated with community changes in the <1-μm and 5- to 1-μm fractions, none of the measured bulk seawater environmental variables are statistically significant in the larger-particle-associated fractions. These results, combined with high particle-associated community variability, especially in the largest size fraction (i.e., >63 μm), suggest that particle composition, including eukaryotes and their associated microbiomes, may be an important factor in selecting for specific particle-associated bacteria.IMPORTANCEBy comparing levels of particle-associated and free-living bacterial diversity at a coastal location over the course of 14 months, we show that bacteria associated with particles are generally more diverse and appear to be less responsive to commonly measured environmental variables than free-living bacteria. These diverse and highly variable particle-associated communities are likely driven by differences in particle substrates both within the water column at a single time point and due to seasonal changes over the course of the year.
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Tu, Chengxu, and Jian Zhang. "Nanoparticle-laden gas flow around a circular cylinder at high Reynolds number." International Journal of Numerical Methods for Heat & Fluid Flow 24, no. 8 (2014): 1782–94. http://dx.doi.org/10.1108/hff-03-2013-0101.
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Purpose – Experiments to investigate the characteristic distribution of nanoparticle-laden gas flow around a circular cylinder were performed with a fast mobility particle spectrometer. The paper aims to discuss these issues. Design/methodology/approach – The fast mobility particle sizer spectrometer is used to measure quasi-instantaneous particle number density. The acquired particle number density, total concentration, and geometric mean diameter at free stream and in the wake were used to discuss the particle characteristic distribution. The time-averaged velocity field detected by particle imaging velocimetry was used to investigate the effect of carried phase on nanoparticles distribution. Findings – Results show that the total particle concentration in the free stream is larger than that in the wake. However, the geometric mean diameter of particle in the free stream is smaller than that in the wake for different Re. The total particle concentration and geometric mean diameter in the free stream and the wake both change in the same way, but with an obvious lag which increases with Re. Despite particle deposition, the number density of particles with electrical-mobility-equivalent diameters in the range from 220.7 to 523.3 nm in the wake is still higher than that in the free stream. Originality/value – Though the particles-laden gas flow around a circular cylinder had been studied experimentally and numerically before, where particles are larger than one micrometer, investigators paid little attention on the nanoparticles-laden gas flow where particles are smaller than one micrometer, especially at high Reynolds number, because numerical methods so far cannot deal these problems completely and satisfactorily. However, this issue is widely existing in nature and engineering application, such as superfine dust or microorganism captured by a circular cylinder model.
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Rivas, M. "Classical particle systems. I. Galilei free particle." Journal of Physics A: Mathematical and General 18, no. 11 (1985): 1971–84. http://dx.doi.org/10.1088/0305-4470/18/11/021.
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Song, Min, Ian Baker, and David M. Cole. "The effect of particles on creep rate and microstructures of granular ice." Journal of Glaciology 54, no. 186 (2008): 533–37. http://dx.doi.org/10.3189/002214308785836959.
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AbstractThe microstructures of particle-free granular freshwater ice and ice containing 1 wt.% of 50 ± 10 mm uniformly distributed particles were investigated before and after compressive creep to ∼10% strain with stresses of 1.45 MPa at −10°C and 0.4 MPa at −5°C. Creep rates of particle-containing ice were always higher than those of particle-free ice. For an initial stress of 1.45 MPa at −10°C, dynamic recrystallization occurred with new grains nucleating and growing along grain boundaries for both sets of specimens, and the ice with particles showed a higher nucleation rate. Under creep with an initial stress of 0.4 MPa at −5°C, dynamic recrystallization also occurred by the nucleation and growth of new grains along the grain boundaries for ice containing particles, but recrystallization in the particle-free ice occurred through grain boundary migration.
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Song, Min, Ian Baker, and David M. Cole. "The effect of particles on dynamic recrystallization and fabric development of granular ice during creep." Journal of Glaciology 51, no. 174 (2005): 377–82. http://dx.doi.org/10.3189/172756505781829287.
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AbstractThe mechanical behavior and microstructural evolution of laboratory-prepared, particle-free fresh-water ice and ice with 1 wt.% (~0.43 vol.%) silt-sized particles were investigated under creep with a stress level of 1.45 MPa at −10°C. The particles were present both within the grains and along the grain boundaries. The creep rates of specimens with particles were always higher than those of particle-free ice. Dynamic recrystallization occurred for both sets of specimens, with new grains nucleating along grain boundaries in the early stages of creep. The ice with particles showed a higher nucleation rate. This resulted in a smaller average grain-size for the ice with particles after a given creep strain. Fabric studies indicated that ice with particles showed a more random orientation of c axes after creep to ~10% strain than the particle-free ice.
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Capponi, Antonio, Steve J. Lane, Jennie S. Gilbert, David G. Macfarlane, Duncan A. Robertson, and Mike R. James. "A novel experimental chamber for the characterization of free-falling particles in volcanic plumes." Review of Scientific Instruments 93, no. 7 (2022): 075105. http://dx.doi.org/10.1063/5.0093730.
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Volcanic plumes pose a hazard to health and society and a particular risk for aviation. Hazard mitigation relies on forecasting plume dispersion within the atmosphere over time. The accuracy of forecasts depends on our understanding of particle dispersion and sedimentation processes, as well as on the accuracy of model input parameters, such as the initial particle size distribution and concentrations of volcanic particles (i.e., volcanic ash) in the atmosphere. However, our understating of these processes and the accurate quantification of input parameters remain the main sources of uncertainty in plume dispersion modeling. It is usually impractical to sample volcanic plumes directly, but particle sedimentation can be constrained in the laboratory. Here, we describe the design of a new experimental apparatus for investigating the dynamics of free-falling volcanic particles. The apparatus can produce a sustained column of falling particles with variable particle concentrations appropriate to a volcanic plume. Controllable experimental parameters include particle size distributions, types, and release rates. A laser-illuminated macrophotography system allows imaging of in-flight particles and their interactions. The mass of landing particles is logged to inform deposition rates. Quantitative measurements include particle morphology characterization, settling velocities, flow rates, and estimation of concentrations. Simultaneous observations of particle interaction processes and settling dynamics through direct control over a wide range of parameters will improve our parameterization of volcanic plume dynamics. Although the apparatus has been specifically designed for volcanological investigations, it can also be used to explore the characteristics of free-falling particle columns occurring in both environmental and industrial settings.
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Rose, Clémence, Karine Sellegri, Isabel Moreno, et al. "CCN production by new particle formation in the free troposphere." Atmospheric Chemistry and Physics 17, no. 2 (2017): 1529–41. http://dx.doi.org/10.5194/acp-17-1529-2017.
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Abstract. Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contributes significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, on Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to ∼ 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between 1 January and 31 December 2012, we found that 61 % of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF, relative to the transport and growth of pre-existing particles, to CCN size. The averaged production of 50 nm particles during those events was 5072, and 1481 cm−3 for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67 % against 53 % in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud-related radiative processes.
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Itoh, Yoshifumi, I. Wuled Lenggoro, Sotiris E. Pratsinis, and Kikuo Okuyama. "Agglomerate-free BaTiO3 particles by salt-assisted spray pyrolysis." Journal of Materials Research 17, no. 12 (2002): 3222–29. http://dx.doi.org/10.1557/jmr.2002.0466.
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Optimum conditions for the synthesis of nonagglomerated BaTiO3 particles by salt-assisted spray pyrolysis (SASP) were investigated. The effect of particle residence time in the reactor and salt concentration on the crystallinity and surface morphology of BaTiO3 was examined by x-ray diffraction and scanning electron microscopy. Mixtures of a metal chloride or nitrate salt, dissolved in aqueous precursor solutions, were sprayed by an ultrasonic atomizer into a five-zone hot-wall reactor. By increasing the salt concentration or the particle residence time in the hot zone, the primary particle size was increased, and its surface texture was improved compared to BaTiO3 particles prepared by conventional spray pyrolysis. The SASP-prepared BaTiO3 crystal was transformed from cubic to tetragonal by simply increasing the salt concentration at constant temperature and residence time. Further thermal treatments such as calcination or annealing are not necessary to obtain nonagglomerated tetragonal BaTiO3 (200–500 nm) particles with a narrow size distribution. Increasing the carrier gas flow rate and decreasing the residence time in the hot zone resulted in cubic BaTiO3 particles about 20 nm in diameter.
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Petrescu, Nicolae, and Florian Ion Tiberiu Petrescu. "Free Particle Spin Speed." American Journal of Engineering and Applied Sciences 12, no. 3 (2019): 337–41. http://dx.doi.org/10.3844/ajeassp.2019.337.341.
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Lin, H., and C. P. Liu. "Interpolation-free particle simulation." Laser and Particle Beams 38, no. 1 (2020): 1–7. http://dx.doi.org/10.1017/s0263034619000806.
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AbstractParticle-in-Cell (PIC) simulation is an interpolation-based method on the Newton–Maxwell (N–M) system. Its well-known drawback is its shape/interpolation functions often causing the violation of continuity equations (CEs) at mesh nodes and that of Maxwell equations (MEs) at particles' positions. Whether this drawback can be overcome by choosing/solving suitable shape/interpolation functions is of fundamental importance for the PIC simulation. Until now, these shape/interpolation functions are usually subjectively chosen and, hence, always invoke the drawback. Here, we first investigate whether these shape/interpolation functions can be self-consistently solved by considering under what condition the CEs and the MEs can be satisfied anywhere. Strict mathematical analysis reveals that strict self-consistent shape/interpolation functions are unavailable. Only few approximately self-consistent shape/interpolation functions are luckily found by some authors. This fact drives us to present another universal interpolation-free strict method on the N–M system.
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Eluru, Gangadhar, Pavan Nagendra, and Sai Siva Gorthi. "Microfluidic In-Flow Decantation Technique Using Stepped Pillar Arrays and Hydraulic Resistance Tuners." Micromachines 10, no. 7 (2019): 471. http://dx.doi.org/10.3390/mi10070471.
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Separating the particles from the liquid component of sample solutions is important for several microfluidic-based sample preparations and/or sample handling techniques, such as plasma separation from whole blood, sheath-free flow focusing, particle enrichment etc. This paper presents a microfluidic in-flow decantation technique that provides the separation of particles from particle-free fluid while in-flow. The design involves the expansion of sample fluid channel in lateral and depth directions, thereby producing a particle-free layer towards the walls of the channel, followed by gradual extraction of this particle-free fluid through a series of tiny openings located towards one-end of the depth-direction. The latter part of this design is quite crucial in the functionality of this decantation technique and is based on the principle called wee-extraction. The design, theory, and simulations were presented to explain the principle-of-operation. To demonstrate the proof-of-principle, the experimental characterization was performed on beads, platelets, and blood samples at various hematocrits (2.5%–45%). The experiments revealed clog-free separation of particle-free fluid for at least an hour of operation of the device and demonstrated purities close to 100% and yields as high as 14%. The avenues to improve the yield are discussed along with several potential applications.
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Nisticò, Giuseppe. "Group Theoretical Derivation of Consistent Free Particle Theories." Foundations of Physics 50, no. 9 (2020): 977–1007. http://dx.doi.org/10.1007/s10701-020-00364-2.
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AbstractThe difficulties of relativistic particle theories formulated by means of canonical quantization, such as those of Klein–Gordon and Dirac, ultimately led theoretical physicists to turn to quantum field theory to model elementary particle physics. In order to overcome these difficulties, the theories of the present approach are developed deductively from the physical principles that specify the system, without making use of canonical quantization. For a free particle these starting assumptions are invariance of the theory and covariance of position with respect to Poincaré transformations. In pursuing the approach, the effectiveness of group theoretical methods is exploited. The coherent development of our program has shown that robust classes of representations of the Poincaré group, discarded by the known particle theories, can in fact be taken as bases for perfectly consistent theories. For massive spin zero particles, six inequivalent theories have been determined, two of which do not correspond to any of the current ones; all of these theories overcome the difficulties of Klein–Gordon one. The present lack of the explicit transformation properties of position with respect to boosts prevents the complete determination of non zero spin particle theories. In the past a particular form of these transformation properties was adopted by Jordan and Mukunda. We check its consistency within the present approach and find that for spin $$\frac{1}{2}$$ 1 2 particles there is only one consistent theory, which is unitarily related to Dirac’s; yet, once again, it requires classes of irreducible representations previously discarded.
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Dang, Minh Triet, Luka Gartner, Peter Schall, and Edan Lerner. "Measuring the free energy of hard-sphere colloidal glasses." Journal of Physics D: Applied Physics 55, no. 16 (2022): 165304. http://dx.doi.org/10.1088/1361-6463/ac4a97.
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Abstract Free energy is a key thermodynamic observable that controls the elusive physics of the glass transition. However, measuring the free energy of colloidal glasses from microscopy images is challenging due to the difficulty of measuring the individual particle size in the slightly polydisperse glassy systems. In this paper, we carry out experiments and numerical simulations of colloidal glasses with the aim to find a practical approach to measure the free energy from colloidal particles at mild polydispersity. We propose a novel method which requires only the particle coordinates from a few confocal microscopy snapshots to estimate the average particle diameter and use it as an input for our experimental free energy measurements. We verify our free energy calculations from Cell Theory with the free energy obtained by Thermodynamic Integration. The excellent agreement between the free energies measured using the two methods close to the glass transition packing fraction highlights the dominant role played by vibrational entropy in determining a colloidal glass’s free energy. Finally, the noticeable free energy difference calculated from uniform and conjectured particle sizes emphasizes the sensitivity on particle free volumes when measuring free energy in the slightly polydisperse colloidal glass.
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Mo, Xiao, Yang Xiao, Kai-Xiong Qing, Feng Zhang, and Hongshi Yu. "Numerical study on the supersonic gas-solid two-phase injection mechanism of needle-free syringe." PLOS One 20, no. 5 (2025): e0322571. https://doi.org/10.1371/journal.pone.0322571.
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Supersonic gas-solid injection technology finds extensive use in drug particle delivery systems. However, the combined impact of particle diameter and mass flow rate on the delivery efficiency remain insufficiently explored. Within the Euler-Lagrange framework, this study utilizes the discrete phase method (DPM) for the numerical simulation of supersonic gas-particle flow in a needle-free injector. After validating the model’s accuracy with experiment results, further investigations were conducted into the influences of particle size and mass flow rate on particle behavior and flow field properties. The results indicate that the impact of larger particles on the compressible structure is stronger, while higher mass flow rate absorbs greater energy from the gas phase, reducing the gas expansion capacity, which results in lower velocity, Mach number, and higher temperature. The jet core zone is approximately x/X = 0.3 in length. Outside core zone, the gas velocity rapidly decays and temperature rises sharply. Within the jet core zone, drug particles are accelerated and cooled, while beyond core zone, they decelerate and heat up. The strongest inter-phase interactions occur primarily in the nozzle expansion area and the jet core zone. Smaller particles reach maximum velocity upstream. This implies that in designing needle-free injectors, the nozzle-to-skin distance must match the drug particle diameter to achieve maximum penetration effectiveness. Furthermore, the particle temperature decreases with smaller sizes. As the particle diameter rises from 10 μm to 100 μm, the minimum temperatures of the particles are 145 K and 264 K, respectively, indicating the need to match the particle diameter with the minimum temperature at which the drug particles remain effective. Additionally, higher mass flow rate doses reduce injection velocity and penetration ability, necessitating the rational control of the administered dose range. These results offer significant theoretical guidance for the design and improvement of needle-free injection.
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Jiang, Lanyue, Peikun Liu, Yuekan Zhang, Xinghua Yang, and Hui Wang. "The Effect of Inlet Velocity on the Separation Performance of a Two-Stage Hydrocyclone." Minerals 9, no. 4 (2019): 209. http://dx.doi.org/10.3390/min9040209.
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The “entrainment of coarse particles in overflow” and the “entrainment of fine particlesin underflow” are two inevitable phenomena in the hydrocyclone separation process, which canresult in a wide product size distribution that does not meet the requirement of a preciseclassification. Hence, this study proposed a two-stage (TS) hydrocyclone, and the effects of the inletvelocity on the TS hydrocyclone were investigated using computational fluid dynamics (CFD).More specifically, the influences of the first-stage inlet velocity on the second-stage swirling flowfield and the separation performance were studied. In addition, the particle size distribution of theproduct was analyzed. It was found that the first-stage overflow contained few coarse particlesabove 40 μm and that the second-stage underflow contained few fine particles. The second-stageunderflow was free of particles smaller than 10 μm and almost free of particles smaller than 20 μm.The underflow product contained few fine particles. Moreover, the median particle size of thesecond-stage overflow product was similar to that of the feed. Inspired by this observation, wepropose to recycle the second-stage overflow to the feed for re-classification and to use only thefirst-stage overflow and the second-stage underflow as products. In this way, fine particle productsfree of coarse particle entrainment, and coarse particle products free of fine particle entrainmentcan be obtained, achieving the goal of precise classification.
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Lin, Xiaohui, Gang Li, Fangchen Xu, et al. "A coupled SPH-DEM approach for modeling of free-surface debris flows." AIP Advances 12, no. 12 (2022): 125018. http://dx.doi.org/10.1063/5.0106333.
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A Lagrangian mesh-less model is proposed to simulate fluid–solid flows with multiple-sized solids, i.e., millimeter-sized particle and larger-sized debris. Considering the difference in the size of solid phases, a hybrid resolved and unresolved model is established based on the coupling method of smoothed particle hydrodynamics (SPH) and discrete element method (DEM). SPH is used to model fluid, and the locally averaged Navier–Stokes equations are adopted as governing equations. DEM is used to model the particle–particle interactions, and the unresolved description of hydrodynamic forces including drag and buoyancy is established. The large-sized debris is modeled as the rigid body, which is discretized by particle elements having both SPH and DEM characteristics, where SPH particle elements are involved in the closure of the SPH fluids, and DEM particle elements interact with the solid particles following the contact law. The numerical model is validated and verified by several examples, including single-particle sedimentation, collapse of cylinder columns, and debris dam break. Results show that the present model reproduces general features of the complex fluid–solid flow with free surfaces. The advantage of the hybrid model is that it can deal with the fluid–solid flow problem with both small particles and large objects at a suitable resolution, and it is especially good at dealing with the free surface flow problem. A discretization for the modeling of debris flows is proposed based on the coupled SPH-DEM method. The novelty of the work is a coupled resolved–unresolved scheme for the free surface flow with multi-sized solids. The present scheme allows using a uniform resolution by bridging the size difference between small-scale solid particles and large-scale debris. The unresolved model of fluid-particle flow is efficient because the fluid resolution can be configured comparably to the particle size. The unified nature of the model allows the combination of resolved and unresolved simulations in the same computational domain.
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Krimi, Abdelkader, Mojtaba Jandaghian, and Ahmad Shakibaeinia. "A WCSPH Particle Shifting Strategy for Simulating Violent Free Surface Flows." Water 12, no. 11 (2020): 3189. http://dx.doi.org/10.3390/w12113189.
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In this work, we develop an enhanced particle shifting strategy in the framework of weakly compressible δ+-SPH method. This technique can be considered as an extension of the so-called improved particle shifting technology (IPST) proposed by Wang et al. (2019). We introduce a new parameter named “ϕ” to the particle shifting formulation, on the one hand to reduce the effect of truncated kernel support on the formulation near the free surface region, on the other hand, to deal with the problem of poor estimation of free surface particles. We define a simple criterion based on the estimation of particle concentration to limit the error’s accumulation in time caused by the shifting in order to achieve a long time violent free surface flows simulation. We propose also an efficient and simple concept for free surface particles detection. A validation of accuracy, stability and consistency of the presented model was shown via several challenging benchmarks.
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Rajagopal, K. R. "Particle-free bodies and point-free spaces." International Journal of Engineering Science 72 (November 2013): 155–76. http://dx.doi.org/10.1016/j.ijengsci.2013.06.002.
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Köhler, Johann Michael, Jonas Jakobus Kluitmann, and Peter Mike Günther. "Metal Nanoparticles as Free-Floating Electrodes." Encyclopedia 1, no. 3 (2021): 551–65. http://dx.doi.org/10.3390/encyclopedia1030046.
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Colloidal metal nanoparticles in an electrolyte environment are not only electrically charged but also electrochemically active objects. They have the typical character of metal electrodes with ongoing charge transfer processes on the metal/liquid interface. This picture is valid for the equilibrium state and also during the formation, growth, aggregation or dissolution of nanoparticles. This behavior can be understood in analogy to macroscopic mixed-electrode systems with a free-floating potential, which is determined by the competition between anodic and cathodic partial processes. In contrast to macroscopic electrodes, the small size of nanoparticles is responsible for significant effects of low numbers of elementary charges and for self-polarization effects as they are known from molecular systems, for example. The electrical properties of nanoparticles can be estimated by basic electrochemical equations. Reconsidering these fundamentals, the assembly behavior, the formation of nonspherical assemblies of nanoparticles and the growth and the corrosion behavior of metal nanoparticles, as well as the formation of core/shell particles, branched structures and particle networks, can be understood. The consequences of electrochemical behavior, charging and self-polarization for particle growth, shape formation and particle/particle interaction are discussed.
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Lin, Wei C., and Huan J. Keh. "Electrophoretic Mobility and Electric Conductivity of Salt-Free Suspensions of Charged Soft Particles." Colloids and Interfaces 5, no. 4 (2021): 45. http://dx.doi.org/10.3390/colloids5040045.
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A unit cell model is employed to analyze the electrophoresis and electric conduction in a concentrated suspension of spherical charged soft particles (each is a hard core coated with a porous polyelectrolyte layer) in a salt-free medium. The linearized Poisson–Boltzmann equation applicable to a unit cell is solved for the equilibrium electrostatic potential distribution in the liquid solution containing the counterions only surrounding a soft particle. The counterionic continuity equation and modified Stokes/Brinkman equations are solved for the ionic electrochemical potential energy and fluid velocity distributions, respectively. Closed-form formulas for the electrophoretic mobility of the soft particles and effective electric conductivity of the suspension are derived, and the effect of particle interactions on these transport characteristics is interesting and significant. Same as the case in a suspension containing added electrolytes under the Debye–Hückel approximation, the scaled electrophoretic mobility in a salt-free suspension is an increasing function of the fixed charge density of the soft particles and decreases with increases in the core-to-particle radius ratio, ratio of the particle radius to the permeation length in the porous layer, and particle volume fraction, keeping the other parameters unchanged. The normalized effective electric conductivity of the salt-free suspension also increases with an increase in the fixed charge density and with a decrease in the core-to-particle radius ratio, but is not a monotonic function of the particle volume fraction.
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Park, Jae-Jung, Yongsoo Kim, Chanmin Lee, et al. "Morphological Analysis of PSMA/PEI Core–Shell Nanoparticles Synthesized by Soap-Free Emulsion Polymerization." Nanomaterials 11, no. 8 (2021): 1958. http://dx.doi.org/10.3390/nano11081958.
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Emulsion polymerization presents the disadvantage that the physical properties of polymer particles are altered by surfactant adsorption. Therefore, in the soap-free emulsion polymerization method, a hydrophilic initiator is utilized while inducing repulsion among particles on the polymer particle surface, resulting in stable polymer particle production. In this study, we developed a methodology wherein spherical and uniform poly(styrene-co-maleic anhydride) (PSMA)/polyethyleneimine (PEI) core–shell nanoparticles were prepared. Further, their morphology was analyzed. During PSMA polymerization, the addition of up to 30% maleic anhydride (MA) resulted in stable polymerization. In PSMA/PEI nanoparticle fabrication, the number of reactants increased with increased initial monomer feed amounts; consequently, the particle size increased, and as the complete monomer consumption time increased, the particle distribution widened. The styrene (St) copolymer acted as a stabilizer, reducing particle size and narrowing particle distribution. Furthermore, the monomers were more rapidly consumed at high initiator concentrations, irrespective of the initiator used, resulting in increased particle stability and narrowed particle distribution. The shell thickness and particle size were PEI feed ratio dependent, with 0.08 being the optimal PEI-to-MA ratio. The fabricated nanoparticles possess immense potential for application in environmental science and in chemical and health care industries.
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Zhang, Jiaoshi, Xianda Gong, Ewan Crosbie, et al. "Stratospheric air intrusions promote global-scale new particle formation." Science 385, no. 6705 (2024): 210–16. http://dx.doi.org/10.1126/science.adn2961.
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New particle formation in the free troposphere is a major source of cloud condensation nuclei globally. The prevailing view is that in the free troposphere, new particles are formed predominantly in convective cloud outflows. We present another mechanism using global observations. We find that during stratospheric air intrusion events, the mixing of descending ozone-rich stratospheric air with more moist free tropospheric background results in elevated hydroxyl radical (OH) concentrations. Such mixing is most prevalent near the tropopause where the sulfur dioxide (SO 2 ) mixing ratios are high. The combination of elevated SO 2 and OH levels leads to enhanced sulfuric acid concentrations, promoting particle formation. Such new particle formation occurs frequently and over large geographic regions, representing an important particle source in the midlatitude free troposphere.
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Lin, J. H., and K. C. Chang. "Particle Dispersion Simulation in Turbulent Flow Due to Particle-Particle and Particle-Wall Collisions." Journal of Mechanics 32, no. 2 (2015): 237–44. http://dx.doi.org/10.1017/jmech.2015.63.
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AbstractSimulation of the 3-D, fully developed turbulent channel flows laden with various mass loading ratios of particles is made using an Eulerian-Lagrangian approach in which the carrier-fluid flow field is solved with a low-Reynolds-number k-ε turbulence model while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. Effects of inter-particle collisions and particle-wall collisions under different extents of wall roughness on particle dispersion are addressed in the study. A cost-effective searching algorithm of collision pair among particles is developed. It is found that the effects of inter-particle collisions on particle dispersion cannot be negligible when the ratio of the mean free time of particle to the mean particle relaxation time of particle is less or equal to O(10). In addition, the wall roughness extent plays an important role in the simulation of particle-wall collisions particularly for cases with small mass loading ratios.
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Visser, Matt. "Quantum mechanix plus Newtonian gravity violates the universality of free fall." International Journal of Modern Physics D 26, no. 12 (2017): 1743027. http://dx.doi.org/10.1142/s0218271817430271.
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Classical point particles in Newtonian gravity obey, as they do in general relativity, the universality of free fall. However, classical structured particles, (for instance with a mass quadrupole moment), need not obey the universality of free fall. Quantum mechanically, an elementary “point” particle (in the particle physics sense) can be described by a localized wave packet, for which we can define a probability quadrupole moment. This probability quadrupole can, under plausible hypotheses, affect the universality of free fall. (So point-like elementary particles, in the particle physics sense, can and indeed must nevertheless have structure in the general relativistic sense once wave packet effects are included.) This raises an important issue of principle, as possible quantum violations of the universality of free fall would fundamentally impact on our ideas of what “quantum gravity” might look like. I will present an estimate of the size of the effect, and discuss where if at all it might be measured.
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Körmendi, F. F. "Kinematical relations at nonlinear laser field: Free electron interactions." Laser and Particle Beams 8, no. 3 (1990): 451–59. http://dx.doi.org/10.1017/s0263034600008685.
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Kinematical relations of nonlinear interaction of laser beams with free charged particles are analyzed. General expressions are found for the number of scattered photons as a function of the number of simultaneously absorbed and/or emitted photons and the kinetic parameters of the charged particle-photon system. The results are applied to the processes of particle acceleration by lasers, frequency conversion, solitonic propagation, and others.
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Ryff, Luiz Carlos. "Interaction-Free Which-Path Information and Some of Its Consequences." Zeitschrift für Naturforschung A 56, no. 1-2 (2001): 155–59. http://dx.doi.org/10.1515/zna-2001-0124.
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Abstract Let us consider a single particle in an interferometer. If one of the two possible paths is blocked and the particle is detected, we know that the particle has followed the path which is not blocked. This would be an interference-free "which-path" information experiment. However, we no longer have an interferometer, since one path is blocked. An alternative is to interact with the particle, but this would change its momentum and as a consequence the interference fringes would disappear, as discussed by Feynman. We can also consider two particles entangled in direction. Knowing the path followed by one of the particles, it is possible to know the path followed by the other. On the other hand, when this information is erased, interference can be observed. However, this is a two particle interference: no single particle interference can be observed. Retrodiction experiments are also possible, but these are not conclusive. Here we propose a much less intuitive experiment in which, without blocking one path or directly interacting with the particle, it is possible to know the path which is being followed by the particle in the interferometer. According to quantum mechanics, this is sufficient to lose the single particle interference. The same idea can be used to test the local pilot wave interpretation, to test quantum nonlocality under new conditions, and to devise an interferometer for a two-photon wave packet. This last result strongly suggests that there must be some connection between the deBroglie wavelength of an N-particle wave packet and entanglement. Wavelength of an /V-particle Wave Packet.
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Li, Kun, Rui Wang, Shuangyun Shao, Fang Xie, Yi Jiang, and Shangran Xie. "Capture Dynamics of Dielectric Microparticles in Hollow-Core-Fiber-Based Optical Traps." Photonics 10, no. 10 (2023): 1154. http://dx.doi.org/10.3390/photonics10101154.
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Optical traps formed in hollow-core fibers (HCFs) can overcome several limitations of conventional free-space optical tweezers. One of the key issues is to load particles from free space into the hollow core with high efficiency, in which process the capture dynamics of the particles in front of the HCF endface plays an important role. In this work, a comprehensive model of the trapping and capture process of the dielectric particles in front of HCF is established by taking into account the features of the fiber modes and the motional parameters of the particles. Stable capture positions are predicted based on analytical calculations of optical forces, and the dependencies of the equilibrium axial trapping position on the beam numerical aperture, the fiber core and particle diameters are provided. In addition, the trajectories and the capture dynamics of the particles are studied by solving the equation of motion for the particles under the impact of optical forces, predicting feasible parameter ranges of the initial amplitude and direction of particle launch velocity for achieving successful particle capture in front of HCF. The results can provide guidance for further improving the particle-loading efficiencies of the HCF-based optical traps, which may find applications of flying particle sensors and long-range particle binding in HCFs.
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Post, Adrian, Erwin Garcia, Eke G. Gruppen, et al. "Higher Free Triiodothyronine Is Associated With Higher HDL Particle Concentration and Smaller HDL Particle Size." Journal of Clinical Endocrinology & Metabolism 107, no. 5 (2022): e1807-e1815. http://dx.doi.org/10.1210/clinem/dgac044.
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Abstract Context Thyroid function status has effects on the development of atherosclerotic cardiovascular disease by affecting lipid metabolism, but associations of high-density lipoprotein (HDL) particle concentrations and subfractions with thyroid hormone levels within the reference range remain elusive. Objective The aim of the present study was to determine the associations of free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) levels with HDL particle characteristics in euthyroid individuals. Methods This cross-sectional study on the associations of thyroid hormones with HDL particle concentrations, HDL subfractions, and HDL particle size included 5844 euthyroid individuals (FT3, FT4, and TSH levels within the reference range and no medication use affecting thyroid function), participating in the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) study. HDL particles and subfractions were measured by nuclear magnetic resonance using an optimized version of the NMR LipoProfile Test (LP4). Results In multivariable linear regression analyses, FT3 was positively associated with total HDL particle concentration (std.β = 0.14; P &lt; 0.001) and with small (std.β = 0.13; P &lt; 0.001) and medium-sized HDL particles (std.β = 0.05; P = 0.001). Conversely, FT3 was inversely associated with large HDL particles (std.β = −0.07; P &lt; 0.001) and with HDL particle size (std.β = −0.08; P &lt; 0.001). Such associations with FT4 or reciprocally with TSH were less pronounced or nonsignificant. Conclusion In euthyroid individuals, higher FT3 is cross-sectionally associated with higher total HDL particle concentration and with lower HDL particle size. These associations may be relevant to better understand the role of HDL in thyroid function–associated atherosclerotic cardiovascular disease.
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Wang, Jintong, Hongyue Men, Jingwei Huang, et al. "Accumulation characteristics of free metallic particles in flowing transformer oil under uniform and non-uniform electric field." Journal of Physics: Conference Series 2369, no. 1 (2022): 012044. http://dx.doi.org/10.1088/1742-6596/2369/1/012044.
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Transformer oil is easily polluted by metal particles. Once the metal particles accumulate in the oil channel, the insulation performance of the equipment will be greatly reduced. In this paper, an oil circulation device was built and the accumulation characteristics of free metal particles in flowing transformer oil were carried out under uniform and non-uniform electric field. The images of particle accumulation process were captured by a high-speed camera. Simultaneously, we analysed the force conditions of particles in oil. And the accumulation mechanisms under different electric fields were discussed combined with the particle trajectories. It was reported that particle accumulation could be observed in static oil under both electric fields. The particle concentration between electrodes decreased gradually with time. However, when the transformer oil was flowing, the accumulation concentration of particles decreased significantly with the increase of flow velocity. The accumulation of metal particles was seriously damaged, even no longer occurred.
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Gray, J. M. N. T., and C. Ancey. "Particle-size and -density segregation in granular free-surface flows." Journal of Fluid Mechanics 779 (August 19, 2015): 622–68. http://dx.doi.org/10.1017/jfm.2015.438.
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When a mixture of particles, which differ in both their size and their density, avalanches downslope, the grains can either segregate into layers or remain mixed, dependent on the balance between particle-size and particle-density segregation. In this paper, binary mixture theory is used to generalize models for particle-size segregation to include density differences between the grains. This adds considerable complexity to the theory, since the bulk velocity is compressible and does not uncouple from the evolving concentration fields. For prescribed lateral velocities, a parabolic equation for the segregation is derived which automatically accounts for bulk compressibility. It is similar to theories for particle-size segregation, but has modified segregation and diffusion rates. For zero diffusion, the theory reduces to a quasilinear first-order hyperbolic equation that admits solutions with discontinuous shocks, expansion fans and one-sided semi-shocks. The distance for complete segregation is investigated for different inflow concentrations, particle-size segregation rates and particle-density ratios. There is a significant region of parameter space where the grains do not separate completely, but remain partially mixed at the critical concentration at which size and density segregation are in exact balance. Within this region, a particle may rise or fall dependent on the overall composition. Outside this region of parameter space, either size segregation or density segregation dominates and particles rise or fall dependent on which physical mechanism has the upper hand. Two-dimensional steady-state solutions that include particle diffusion are computed numerically using a standard Galerkin solver. These simulations show that it is possible to define a Péclet number for segregation that accounts for both size and density differences between the grains. When this Péclet number exceeds 10 the simple hyperbolic solutions provide a very useful approximation for the segregation distance and the height of rapid concentration changes in the full diffusive solution. Exact one-dimensional solutions with diffusion are derived for the steady-state far-field concentration.
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Kepner, Gordon R. "Relating the deBroglie and Compton Wavelengths to the Velocity of Light?" Applied Physics Research 10, no. 4 (2018): 102. http://dx.doi.org/10.5539/apr.v10n4p102.
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No report in the literature has directly described this relation. New constants for particles are presented. One relates to the Compton wavelength, called here the “mass-wave” constant for all particles. The other relates to the deBroglie wavelength, called here the “velocity-wave” constant for a particle. An equation is derived based on these two constants encapsulating a fundamental relation between the matter-states, particle and wave, to the velocity of light. New approaches to the Uncertainty relations are shown. The basic Schrodinger equation is derived from the perspective of a non-dimensional second-order differential equation free of any assumed empirical constants. The resulting time-dependent wave equation for a free particle was then expressed in terms of the particle velocity and deBroglie wavelength.
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Зарипов, Д. И., М. П. Токарев, А. А. Лукьянов, and Д. М. Маркович. "Grid-free planar method of Particle Image Velocimetry." Numerical Methods and Programming (Vychislitel'nye Metody i Programmirovanie), no. 4 (October 15, 2022): 328–38. http://dx.doi.org/10.26089/nummet.v23r420.
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На сегодняшний день многопроходный метод PIV (Particle Image Velocimetry) широко используется в области экспериментальной механики жидкости и газа из-за его высокой надежности при решении практических задач. Однако он имеет известное ограничение, связанное с ошибками, возникающими при вычислении производных скорости, необходимых для деформации обрабатываемых PIV-изображений при повышении производительности метода. Поскольку количество ошибок увеличивается с применением схем более высокого порядка, на практике чаще всего ограничиваются первым порядком, что в свою очередь приводит к снижению пространственного разрешения. В данной работе предлагается метод, допускающий применение схем более чем второго порядка, что позволяет заметно повысить точность измерения скорости и ее производных и тем самым увеличить пространственное разрешение. Метод не требует восстановления ошибочных векторов скорости, позволяет избежать численного расчета производных скорости и легко применим на практике. Today, the method of PIV (Particle Image Velocimetry) is widely used in the field of experimental fluid mechanics due to its high reliability in solving practical problems. However, it has a known limitation associated with errors that occur when calculating velocity derivatives, which are necessary to deform the processed PIV images while improving the performance of the method. Since the number of errors increases with the use of higher order schemes, in practice it is most often limited to the first order, which in turn leads to a decrease in spatial resolution. In the present research, we propose a method that allows the schemes of more than the second order, which significantly improves the accuracy of measuring velocity and its derivatives, and thereby increases the spatial resolution. The method does not require the recovery of erroneous velocity vectors, avoids the numerical calculation of velocity derivatives, and is easily applied in practice.
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Bożejko, Marek, José Luís da Silva, Tobias Kuna, and Eugene Lytvynov. "Approximation of a free Poisson process by systems of freely independent particles." Infinite Dimensional Analysis, Quantum Probability and Related Topics 21, no. 03 (2018): 1850020. http://dx.doi.org/10.1142/s0219025718500200.
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Let [Formula: see text] be a non-atomic, infinite Radon measure on [Formula: see text], for example, [Formula: see text] where [Formula: see text]. We consider a system of freely independent particles [Formula: see text] in a bounded set [Formula: see text], where each particle [Formula: see text] has distribution [Formula: see text] on [Formula: see text] and the number of particles, [Formula: see text], is random and has Poisson distribution with parameter [Formula: see text]. If the particles were classically independent rather than freely independent, this particle system would be the restriction to [Formula: see text] of the Poisson point process on [Formula: see text] with intensity measure [Formula: see text]. In the case of free independence, this particle system is not the restriction of the free Poisson process on [Formula: see text] with intensity measure [Formula: see text]. Nevertheless, we prove that this is true in an approximative sense: if bounded sets [Formula: see text] ([Formula: see text]) are such that [Formula: see text] and [Formula: see text], then the corresponding particle system in [Formula: see text] converges (as [Formula: see text]) to the free Poisson process on [Formula: see text] with intensity measure [Formula: see text]. We also prove the following [Formula: see text]-limit: Let [Formula: see text] be a deterministic sequence of natural numbers such that [Formula: see text]. Then the system of [Formula: see text] freely independent particles in [Formula: see text] converges (as [Formula: see text]) to the free Poisson process. We finally extend these results to the case of a free Lévy white noise (in particular, a free Lévy process) without free Gaussian part.
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Li, Chengbo, Shuqing Yang, Gan Luo, Hengbin Liao, and Jun Du. "Revealing the Nuclei Formation in Carbon-Inoculated Mg-3%Al Alloys Containing Trace Fe." Materials 12, no. 15 (2019): 2478. http://dx.doi.org/10.3390/ma12152478.
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In this study, Fe-bearing Mg-3%Al alloys were inoculated by combining carbon with or without Ca. Both processes can significantly refine the grain size of Mg-3%Al alloys. The highest refining efficiency can be obtained by carbon combined with Ca. The synergistic grain refining efficiency can be attributed to the constitutional undercooling produced by the addition of Ca. Two kinds of carbon-containing nuclei with duplex-phase particles and cluster particles were observed in the carbon-inoculated alloys. A thermodynamic model was established to disclose the formation mechanisms of the duplex-phase particles and Al4C3 cluster particles. This thermodynamic model is based on the change of Gibbs free energy for the formation of these two kinds of particles. The calculated results show that these two particles can form spontaneously, since the change of Gibbs free energy is negative. However, the Gibbs free change of the duplex-phase particle is more negative than the Al4C3 cluster particle. This indicates that the adsorption process is more spontaneous than the cluster process, and tiny Al4C3 particles are preferred to form duplex-phase particle, rather than gathering to form an Al4C3 cluster particle. In addition, the addition of Ca can reduce the interfacial energy between the Al4C3 phase and the Al–Fe phase and promote the formation of duplex-phase particles.
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Li, Joshua Qing Song, Yan Qiu Wang, and Hai Wang. "Preparation and Characterization of Silica/Polymer Hybrid Submicron Particles via a Semi-Continuous Soap-Free Emulsion Polymerization." Advanced Materials Research 1120-1121 (July 2015): 225–32. http://dx.doi.org/10.4028/www.scientific.net/amr.1120-1121.225.
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Submicron hybrid particles were prepared by direct polymerization of three monomers of styrene, methyl methacrylate (MMA), and vinyl acetate (VAC) onto the hydrophilic surface of 230 nm silica submicron particles without any coupling agent in a semi-continuous emulsifier-free emulsion polymerization at a monomer starved condition. The polymerization was initiated by potassium persulfate with constant monomer feed at 0.01, 0.02, or 0.04 mL/min, after adding 230 nm silica seed particles. The particle growth was investigated with a laser particle size analyzer and SEM, and the particle surfaces by Fourier transform infrared spectroscopy (FT-IR). It was founded that the growth of the hybrid particles depended on the hydrophobic characteristics of the polymers. When monomer was the most hydrophobic styrene, polystyrene (PS) shells split off from the hydrophilic surface of the unmodified silica particle whenever the shells reached a limit of ~20 nm. However, both polymethyl methacrylate (PMMA) and polyvinyl acetate (PVAC) shells grew constantly on the hydrophilic surface of silica particles. In the process of the whole reaction, the SiO2/PMMA and SiO2/PVAC hybrid particles kept almost monodisperse.
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KAWANAMI, Hidehiro, Koichiro OGATA, Katsuya FUNATSU, and Yuji TOMITA. "Effect of Particle Diameter on the Free Falling of Particles." Proceedings of Conference of Kyushu Branch 2002.55 (2002): 165–66. http://dx.doi.org/10.1299/jsmekyushu.2002.55.165.
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Wu, Di, Nan Jiang, Wenbo Du, Ke Tang, and Xianbin Cao. "Particle Swarm Optimization with Moving Particles on Scale-Free Networks." IEEE Transactions on Network Science and Engineering 7, no. 1 (2020): 497–506. http://dx.doi.org/10.1109/tnse.2018.2854884.
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Jonitz-Heincke, Anika, Jenny Tillmann, Melanie Ostermann, et al. "Label-Free Monitoring of Uptake and Toxicity of Endoprosthetic Wear Particles in Human Cell Cultures." International Journal of Molecular Sciences 19, no. 11 (2018): 3486. http://dx.doi.org/10.3390/ijms19113486.
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The evaluation of the biological effects of endoprosthetic wear particles on cells in vitro relies on a variety of test assays. However, most of these methods are susceptible to particle-induced interferences; therefore, label-free testing approaches emerge as more reliable alternatives. In this study, impedance-based real-time monitoring of cellular viability and metabolic activity were performed following exposure to metallic and ceramic wear particles. Moreover, label-free imaging of particle-exposed cells was done by high-resolution darkfield microscopy (HR-ODM) and field emission scanning electron microscopy (FESEM). The isolated human fibroblasts were exposed to CoCr28Mo6 and alumina matrix composite (AMC) ceramic particles. HR-ODM and FESEM revealed ingested particles. For impedance measurements, cells were seeded on gold-plated microelectrodes. Cellular behavior was monitored over a period of 48 h. CoCr28Mo6 and AMC particle exposure affected cell viability in a concentration-dependent manner, i.e., 0.01 mg/mL particle solutions led to small changes in cell viability, while 0.05 mg/mL resulted in a significant reduction of viability. The effects were more pronounced after exposure to CoCr28Mo6 particles. The results were in line with light and darkfield microcopy observations indicating that the chosen methods are valuable tools to assess cytotoxicity and cellular behavior following exposure to endoprosthetic wear particles.
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Gnatenko, Kh P., H. P. Laba, and V. M. Tkachuk. "Features of free particles system motion in noncommutative phase space and conservation of the total momentum." Modern Physics Letters A 33, no. 23 (2018): 1850131. http://dx.doi.org/10.1142/s0217732318501316.
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Influence of noncommutativity on the motion of composite system is studied in noncommutative phase space of canonical type. A system composed by N free particles is examined. We show that because of the momentum noncommutativity free particles of different masses with the same velocities at the initial moment of time do not move together. The trajectory and the velocity of a free particle in noncommutative phase space depend on its mass. So, a system of the free particles flies away. Also, it is shown that the total momentum defined in the traditional way is not integral of motion in a space with noncommutativity of coordinates and noncommutativity of momenta. We find that in the case when parameters of noncommutativity corresponding to a particle are determined by its mass, the trajectory and the velocity of the free particles are independent of the mass. Also, the total momenta as integrals of motion can be introduced in noncommutative phase space.
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Trieu, Hang, Per Bergström, Mikael Sjödahl, J. Gunnar I. Hellström, Patrik Andreasson, and Henrik Lycksam. "Photogrammetry for Free Surface Flow Velocity Measurement: From Laboratory to Field Measurements." Water 13, no. 12 (2021): 1675. http://dx.doi.org/10.3390/w13121675.
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This study describes a multi-camera photogrammetric approach to measure the 3D velocity of free surface flow. The properties of the camera system and particle tracking velocimetry (PTV) algorithm were first investigated in a measurement of a laboratory open channel flow to prepare for field measurements. The in situ camera calibration methods corresponding to the two measurement situations were applied to mitigate the instability of the camera mechanism and camera geometry. There are two photogrammetry-based PTV algorithms presented in this study regarding different types of surface particles employed on the water flow. While the first algorithm uses the particle tracking method applied for individual particles, the second algorithm is based on correlation-based particle clustering tracking applied for clusters of small size particles. In the laboratory, reference data are provided by particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). The differences in velocities measured by photogrammetry and PIV, photogrammetry and LDV are 0.1% and 3.6%, respectively. At a natural river, the change of discharges between two measurement times is found to be 15%, and the corresponding value reported regarding mass flow through a nearby hydropower plant is 20%. The outcomes reveal that the method can provide a reliable estimation of 3D surface velocity with sufficient accuracy.
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Miffre, Alain, Danaël Cholleton, Tahar Mehri, and Patrick Rairoux. "Remote Sensing Observation of New Particle Formation Events with a (UV, VIS) Polarization Lidar." Remote Sensing 11, no. 15 (2019): 1761. http://dx.doi.org/10.3390/rs11151761.
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Observations of new particle formation events in free troposphere are rather seldom and limited in time and space, mainly due to the complexity and the cost of the required on-board instrumentation for airplane field campaigns. In this paper, a calibrated (UV, VIS) polarization elastic lidar (2β + 2δ) is used to remotely sense new particle formation events in the free troposphere in the presence of mineral dust particles. Using very efficient (UV, VIS) light polarization discriminators (1:107) and after robust calibration, the contribution of mineral dust particles to the co-polarized (UV, VIS) lidar channels could be removed, to reveal the backscattering coefficient of the newly nucleated particles after these numerous particles have grown to a size detectable with our lidar. Since our polarization and wavelength cross-talks are fully negligible, the observed variation in the (UV, VIS) particle backscattering time–altitude maps could be related to variations in the particle microphysics. Hence, day and nighttime differences, at low and high dust loadings, were observed in agreement with the observed nucleation process promoted by mineral dust. While light backscattering is more sensitive to small-sized particles at the UV lidar wavelength of 355 nm, such new particle formation events are here for the first time also remotely sensed at the VIS lidar wavelength of 532 nm at which most polarization lidars operate. Moreover, by addressing the (UV, VIS) backscattering Angstrom exponent, we could discuss the particles’ sizes addressed with our (UV, VIS) polarization lidar. As nucleation concerns the lowest modes of the particles’ size distribution, such a methodology may then be applied to reveal the lowest particle sizes that a (UV, VIS) polarization lidar can address, thus improving our understanding of the vertical and temporal extent of nucleation in free troposphere, where measurements are rather seldom.
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Moalem, A., and A. Gersten. "Common Features of Free Particle Wave Functions in Curved Space-times." Journal of Physics: Conference Series 2482, no. 1 (2023): 012003. http://dx.doi.org/10.1088/1742-6596/2482/1/012003.
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Abstract Quantum equations for massless particles of any spin and for massive spin one-half particles are considered in curved space-times. It is demonstrated that in stationary axially symmetric space-times the angular wave functions up to a normalization function are the same as in a Minkowski space-time. The radial wave functions satisfy second order nonhomogeneous differential equations with three nonhomogeneous terms which depend in a unique form on the ratio of time to space curvatures. For a Dirac spin one-half particle, in addition to these three terms a fourth term which depends on the particle rest mass is added.
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Arangio, Andrea M., Haijie Tong, Joanna Socorro, Ulrich Pöschl, and Manabu Shiraiwa. "Quantification of environmentally persistent free radicals and reactive oxygen species in atmospheric aerosol particles." Atmospheric Chemistry and Physics 16, no. 20 (2016): 13105–19. http://dx.doi.org/10.5194/acp-16-13105-2016.
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Abstract. Fine particulate matter plays a central role in the adverse health effects of air pollution. Inhalation and deposition of aerosol particles in the respiratory tract can lead to the release of reactive oxygen species (ROS), which may cause oxidative stress. In this study, we have detected and quantified a wide range of particle-associated radicals using electron paramagnetic resonance (EPR) spectroscopy. Ambient particle samples were collected using a cascade impactor at a semi-urban site in central Europe, Mainz, Germany, in May–June 2015. Concentrations of environmentally persistent free radicals (EPFR), most likely semiquinone radicals, were found to be in the range of (1–7) × 1011 spins µg−1 for particles in the accumulation mode, whereas coarse particles with a diameter larger than 1 µm did not contain substantial amounts of EPFR. Using a spin trapping technique followed by deconvolution of EPR spectra, we have also characterized and quantified ROS, including OH, superoxide (O2−) and carbon- and oxygen-centered organic radicals, which were formed upon extraction of the particle samples in water. Total ROS amounts of (0.1–3) × 1011 spins µg−1 were released by submicron particle samples and the relative contributions of OH, O2−, C-centered and O-centered organic radicals were ∼ 11–31, ∼ 2–8, ∼ 41–72 and ∼ 0–25 %, respectively, depending on particle sizes. OH was the dominant species for coarse particles. Based on comparisons of the EPR spectra of ambient particulate matter with those of mixtures of organic hydroperoxides, quinones and iron ions followed by chemical analysis using liquid chromatography mass spectrometry (LC-MS), we suggest that the particle-associated ROS were formed by decomposition of organic hydroperoxides interacting with transition metal ions and quinones contained in atmospheric humic-like substances (HULIS).
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Li, Date, Huaixin Zhang, and Guangfei Qin. "A Modified MPS Method with a Split-Pressure Poisson Equation and a Virtual Particle for Simulating Free Surface Flows." Journal of Marine Science and Engineering 11, no. 1 (2023): 215. http://dx.doi.org/10.3390/jmse11010215.
Full textAbstract:
As a Lagrangian mesh-free method, the moving particle semi-implicit (MPS) method can easily handle complex incompressible flow with a free surface. However, some deficiencies of the MPS method, such as inaccurate results, unphysical pressure oscillation, and particle thrust near the free surface, still need to be further resolved. Here, we propose a modified MPS method that uses the following techniques: (1) a modified MPS scheme with a split-pressure Poisson equation is proposed to reproduce hydrostatic pressure stably; (2) a new virtual particle technique is developed to ensure the symmetrical distribution of particles on the free surface; (3) a Laplacian operator that is consistent with the original gradient operator is introduced to replace the original Laplacian operator. In addition, a two-judgment technique for distinguishing free surface particles is introduced in the proposed MPS method. Four free surface flows were adopted to verify the proposed MPS method, including two hydrostatic problems, a dam-breaking problem, and a violent sloshing problem. The enhancement of accuracy and stability by these improvements was demonstrated. Moreover, the numerical results of the proposed MPS method showed good agreement with analytical solutions and experimental results.